cancellable promise.js

import Promise from 'bluebird'

Promise.config({
    warnings: false,
    cancellation: true,
})

const convertJson = string => {
    try {
        return JSON.parse(string);
    } catch (e) {
        return string;
    }
}

let lastRequest = null

const request = url => {
    if (lastRequest) {
        lastRequest.cancel()
    }
    const promise = new Promise((resolve, reject, onCancel) => {
        const xhr = new XMLHttpRequest()

        xhr.onload = () => {
            setTimeout(function() {
                resolve({
                    status: xhr.status,
                    data: convertJson(xhr.responseText)
                })
            }, 1000);
        }
        xhr.onerror = () => reject('rejected')
        xhr.open('GET', url, true)
        xhr.send(null)

        onCancel(() => {
            console.log('cancelled');
            xhr.abort()
        });
    })

    lastRequest = promise

    return promise
}

const button = document.createElement('button')
button.innerHTML = 'Button'

document.body.appendChild(button)

button.addEventListener('click', () => {
    const data = request('https://jsonplaceholder.typicode.com/posts')
        .then(console.log)
        .catch(console.error)
})